Smart home environments have been introduced to monitor health and wellbeing of elderly people who are losing their ability to live independently. Such systems typically comprise a plurality of sensors mounted at a variety of places in the home for the monitoring of everyday activities. For example, PIR sensors may be mounted in one or more rooms to detect the presence or movement of persons within those spaces.
One common feature of such systems is the provision of one or more sensor arrangements for the monitoring of opening or closing of doors. For example, such sensor arrangements incorporated to a front door may be used to detect whether and when an elderly person is leaving the house, for example at unusual or dangerous times. In another example, sensors may be mounted to a bathroom or toilet door so that bathing and toileting behavior may be monitored. Attached to kitchen cupboards, cabinets and drawers or even a refrigerator door or bread bin, such sensors may be used to provide information about eating habits.
The monitoring of the opening and closing of doors in this way may be performed by mechanical door switches. These are mounted either to a door frame or to a door itself and are mechanically activated when a door is fully closed, and mechanically released when a door is opened.
One disadvantage of mechanical door switches is that while they are reliable for the detection of a door being fully closed or not fully closed, they cannot be used to monitor other kinds of partial opening or closing events. For example, it would be desirable to be able to detect the movement of a door from partially open to fully open, or from being slightly ajar to being more fully ajar. Likewise, it is desirable to have the capacity to detect closing events even if a door is not pushed fully shut.
Another disadvantage of mechanical switches is that they require installation by a skilled person in order to ensure that the switch neither obstructs the full closure of the door, nor misses contact with the door altogether.
Typically, these problems are overcome by use instead of a sensor which is attached to a door or drawer and which has the capacity to detect or inform about acceleration, for example an accelerometer or a magnetometer. These do not require special skills to install and may be mounted, for example by a care giver, to any part of the door or drawer in interest.
However, a major drawback of state-of-the art acceleration based door sensors is a generally poor reliability in detecting opening and closing events. Output signals from sensors mounted to movable objects may exhibit peak intensities comparable to that of the noise level or signal fluctuations unrelated to the opening or closing event.
US 2013/327142 discloses a way to detect the opening of a door with force, based on a measurement of acceleration and comparison with thresholds. This system is only able to detect violent movement and is not able to detect normal opening and closing events.
A method would be desirable therefore of detecting from the output signal of a movement sensor, the normal opening and closing of a door or drawer to which the sensor is mounted, wherein these movement events are reliably and accurately extricated from background noise carried by the signal.